let a1:any = 111;
let b1:string = a1;
console.log(b1);

// unkonwn不可以像any一样直接转化为string类型,但可以用as转化为string类型
let c1:unknown = "abc";
let d1:string = c1 as string;
console.log(d1);

let e1:string = '99';
// 不可以将字符串类型直接转化为数值类型，要用unknown过渡一下
let f1:number = e1 as unknown as number;
console.log(f1);